Python3 got a lot of flac for the decision to break away from it's byte sequences, to it's a unicode string. But I think that was the right choice. I still understand why people writing software that only cared about network, on-the-wire, pretend-to-be-text type strings.

Then again, based on some other comments here, apparently there are still some dark corners:

    Python 3.2.3 (default, Feb 20 2013, 14:44:27) 
    [GCC 4.7.2] on linux2
    >>> s="Åßẞ"
    >>> s == s.upper().lower()
    False
    >>> s.lower()
    'åßß'

    Python 3.4.2 (default, Dec 27 2014, 13:16:08)
    [GCC 4.9.2] on linux
    >>> s="Åßẞ"
    >>> s.lower()
    'åßß'
    >>> s.lower().upper()
    'ÅSSSS'
    >>> s == s.lower().upper()
    False
    >>> s.lower().upper() == 'ÅSSSS'
    True
    >>> 'SS'.lower()
    'ss'
    >>> 'ß'.lower()
    'ß'
    >>> 'ß'.lower().upper()
    'SS'
    >>> 'ß'.lower().upper().lower()
    'ss'